Grain Equivalents in Corn Silage: An Update on Hybrids

Joe Lauer, Corn Agronomist

Environment significantly affects the amount of grain in corn silage. This year's (2006) drought affected pollination reducing both grain yield and plant stature. Last year's (2005), drought reduced plant stature, but grain yields were at record levels. Following the 2005 growing season, farmers would sometimes talk about corn silage being "hot" when fed to livestock, meaning that there was too much grain compared to stover (grain equivalents) in the silage.

Dairymen and corn farmers need to understand the grain equivalent relationship when acres are contracted for silage production. This relationship is dynamic and, as we are learning, quite variable to the extent that one predetermined value should probably not be used in contracts. In addition, grain equivalents are used to calculate loan deficiency payments (LDP) with a value between 7 and 8 bu/T often used for these calculations.

In 2004 and 2005, six corn hybrids were grown at six locations. Hybrid types included bmr, leafy, transgenic, and normal hybrids. Each hybrid was replicated 3 times and grown in 8-row plots, with 4 rows used for silage harvest, and 4 rows used later at grain harvest.

On average, hybrids across locations and years produced grain equivalents of 7.5 bu/T (bushels of grain at 15.5% moisture per ton of corn silage at 65% moisture). The range among environment averages was 2.3 bu/T (min.= 6.3 bu/T, max.= 8.6 bu/T). The range among hybrids for grain equivalents was 6 bu/T (min.= 4.5 bu/T, max.= 10.5 bu/T). Grain equivalents tended to be higher at Arlington and Galesville in 2005 (drought early) than 2004 (normal). The average range among hybrids for an environment was 2.1 bu/T (max.= Rhinelander 2005= 3.6 bu/T, min.= Valders 2004= 1.2 bu/T).

Given the wide range in grain equivalents among hybrids between and within environments, it is reasonable that dairymen and grain farmers should devise alternative methods for calculating the amount of grain in corn silage. It would be best to negotiate contracts based upon silage quality, rather than grain equivalents or forage yield.

Table 1. Location and year effect on grain equivalents (bu/T) contained in  corn silage for six corn hybrids.
Location Year Average Minimum hybrid Maximum hybrid
    bushels of grain (15.5% moisture) per
Ton of corn silage (65% moisture)
Arlington 2004 7.7 6.5 8.3
  2005 8.6 7.8 10.5
Fond du Lac 2005 7.0 6.0 7.5
Galesville 2004 7.2 5.8 8.2
  2005 8.0 7.0 8.8
Marshfield 2004 7.0 5.5 7.7
  2005 6.3 4.5 7.2
Rhinelander 2005 7.7 6.7 10.3
Valders 2004 7.8 7.0 8.2
  2005 7.5 6.5 8.0
Average --- 7.5 6.4 8.5

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